This invention relates generally to control knobs and is concerned more particularly with a knob having means for preventing accidental rotation of a critical adjustment shaft.
The operation of equipment today is controlled, to a great extent, by rotationally adjustable devices, such as valves, timers, rheostats, potentiometers, rotary capacitors, gang switches and the like. Such devices generally comprise a body having protruding therefrom a threaded collar through which extends a rotatable adjustment shaft. Thus, a device of the described type may be mounted on the rear surface of a control panel having an aligned hole through which the threaded collar and rotatable shaft protrude. Accordingly, on the front surface of the panel, the threaded collar may be engaged by a suitable fastener, such as a hex nut, for example, to secure the device to the rear surface of the panel; and the distal end portion of the shaft may have affixed thereto a suitable control knob.
However, a critically adjusted control device of the described type generally is mounted in a more remote portion of the equipment, such as in the rear of a console, for example. Thus, the critical device may be reached for adjustment by a skilled technician only after opening a rear door of the console or removing a safety interlocked cover of the equipment, for examples. Also, in order to avoid variation of the adjustment due to shock or vibration, the device may be provided with a locking means for holding the rotatable shaft in an adjusted position. Further, such critically adjusted devices generally require an accessory tool such as a screw driver, for example, in order to effect the desired adjustment. Consequently, the critically adjusted control device is not readily accessible to a skilled technician for timely adjustment, when required.
Therefore, it would be advantageous and desirable to provide a control device with a knob having means for preventing accidental adjustment thereof and which, consequently, may be mounted on the readily accessible control panel.